What I do:

I prepare Ubuntu live USB and boot with it. I select the USB pen drive. The PC tries to boot from it.

What happens

I receive an error message: boot error.

What is expected:

A normal boot procedure.

Some other information:

1) No matter how I prepare the USB, I get the same result. The USB works just fine on some other PC.

2) The PC will boot from USB made to boot MS-DOS.

3) The PC is dual-boot, Win7 and Ubuntu(installed from CD)

4) The BIOS is Phoenix-Award(version of bios dated 2008), the motherboard is comparatively new.